expression: cleanup expr_ops_by_type() and handle u32 input

Make fewer assumptions about the underlying integer type of the enum.
Instead, be clear about where we have an untrusted uint32_t from netlink
and an enum. Rename expr_ops_by_type() to expr_ops_by_type_u32() to make
this clearer. Later we might make the enum as packed, when this starts
to matter more.

Also, only the code path expr_ops() wants strict validation and assert
against valid enum values. Move the assertion out of
__expr_ops_by_type(). Then expr_ops_by_type_u32() does not need to
duplicate the handling of EXPR_INVALID. We still need to duplicate the
check against EXPR_MAX, to ensure that the uint32_t value can be cast to
an enum value.

[ Remove cast on EXPR_MAX. --pablo ]

Signed-off-by: Thomas Haller <thaller@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/netlink.c b/src/netlink.c
index 70ebf382..8af579c7 100644
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -878,8 +878,8 @@ static struct expr *set_make_key(const struct nftnl_udata *attr)
 {
 	const struct nftnl_udata *ud[NFTNL_UDATA_SET_TYPEOF_MAX + 1] = {};
 	const struct expr_ops *ops;
-	enum expr_types etype;
 	struct expr *expr;
+	uint32_t etype;
 	int err;
 
 	if (!attr)
@@ -895,7 +895,7 @@ static struct expr *set_make_key(const struct nftnl_udata *attr)
 		return NULL;
 
 	etype = nftnl_udata_get_u32(ud[NFTNL_UDATA_SET_TYPEOF_EXPR]);
-	ops = expr_ops_by_type(etype);
+	ops = expr_ops_by_type_u32(etype);
 	if (!ops)
 		return NULL;